US4973457A
Expired / Lapsed
US
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Method for the reduction of nitrogen oxide
Assignee: Norsk Hydro ASA
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Filing: 1989-09-06
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Granted: 1990-11-27
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Expires: 2009-09-06
Abstract
Abstract The present invention relates to a method of reduction of nitrogen oxides in gas mixtures, especially the removal/decomposition of nitrogen oxide in hot combustion gases. The hot gas mixture which contains N 2 O is given a retention time of 0.1-3 seconds before being cooled down. About 90% of N 2 O is thereby decomposed to N 2 and O 2 . A hot gas mixture formed by catalytic combustion of ammonia is given a retention time of 0.5-2 seconds before it is cooled in a heat recovery unit. The combustion gases can also be brought in contact with a metal or metal oxide catalyst for selective decomposition of the N 2 O.
Inventors
- 👤 Gunnar Kongshaug
- 👤 Leif Hjornevik
- 👤 Erik Fareid
- 👤 Oystein Nirisen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 07:15
CPC Classifications
B; B01; B01D; B01D53/00; B01D53/34; B01D53/46; B01D53/54; B01D53/56; Y; Y02; Y02C; Y02C20/00; Y02C20/10
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
79 words
A method of reduction of dinitrogen oxide formed during catalytic combustion of ammonia and oxygen to nitrogen oxides in a combustion unit, which are then cooled in a heat recovery unit and absorbed in an absorption unit having water or diluted nitric acid or both therein, said method comprising giving the high temperature combustion gases formed during said catalytic combustion a retention time of 0.1-3 seconds before said high temperature combustion gases are cooled by said heat recovery unit.
Claim 2
Independent Claim
79 words
A method of reduction of dinitrogen oxide formed during catalytic combustion of ammonia and oxygen to nitrogen oxides in a combustion unit, which are then cooled in a heat recovery unit and absorbed in an absorption unit having water or diluted nitric acid or both therein, said method comprising giving the high temperature combustion gases formed during said catalytic combustion a retention time of 0.1-3 seconds before said high temperature combustion gases are cooled by said heat recovery unit.
Claim 3
Dependent Claim
41 words
The method of claim 1, wherein: said high temperature combustion gases formed during said catalytic combustion are given a retention time of 0.5-2 seconds in said combustion unit before said high temperature combustion gases are cooled by said heat recovery unit.
Claim 4
Dependent Claim
29 words
The method of claim 1, wherein: said high temperature combustion gases are brought in contact with a metal or metal oxide catalyst for selective decomposition of N 2 O.
Claim 5
Dependent Claim
28 words
The method of claim 1, wherein: gases leaving said absorption unit are brought in contact with a metal or metal oxide catalyst for decomposition of N 2 O.
References Cited (Backward Citations)
US3489515A
Cited
NL8006262A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-11-26 | 1994-05-28 | 1994-11-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-11-26 | 1998-05-28 | 1998-11-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-11-26 | 2002-05-28 | 2002-11-27 | $7700.00 | Window Closed / Lapsed |